JPH0368974A - Developing device - Google Patents

Abstract

PURPOSE:To widen a margin for discharge and to perform uniform development with desired density by coating the surface of a developing roller with a material having specified resistivity. CONSTITUTION:A blade 24 is allowed to press-contact with the developing roller 21. The developer layer of color toner, etc., is formed on the roller 21 and it is opposed to an electrostatic latent image on a photosensitive drum 2 to perform development. In such the case, a roll where a coating layer 40 consisting of the material whose resistivity is 10<3>-10<11>OMEGA.cm is formed on its surface is used as the roller 21. Since semiconductor glass, SiC and A-Si, etc., can be used for the above material and the material is allowed to have resistance to such an extent that current concentration for maintaining the discharge is not passed, the margin for discharge is widened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a developing device applied to an image forming apparatus such as a color printer.

(Prior art) In recent years, non-magnetic
Products using component developers are becoming more pointed. This type of developing device can be significantly smaller and lighter than one using a two-component developer consisting of toner and carrier. Furthermore, since no carrier is used, the photoreceptor drum and transfer drum are not damaged. Furthermore, since it is non-contact development, no jitter occurs. In addition, magnetic toner, especially when used in color printers, suffers from poor color rendering properties due to the presence of magnetic powder mixed in the toner, but it has various advantages such as not having such problems.

Usually, this type of developing device has a configuration as shown in FIG. In the figure, a is a developing roller, b is an elastic foam roller,
C is an aluminum roller.

A non-magnetic component developer (hereinafter referred to as toner) t in a container d is carried to the right in the figure by an aluminum roller C and an elastic foam roller b, is drawn up by a developing roller a, and is transferred between the developing roller a and the toner. The developing roller a is fed between the developing roller a and the blade e which is in pressure contact with the developing roller a. Here, the toner t is made into a thin layer and charged, and then the toner t is made into a thin layer and charged.
photoreceptor drum) is sent out to the f side.

At this time, -250V is applied to the developing roller a.

Since ACl and a bias of 4 KV are applied, the toner t is directed toward the exposed area of the photoreceptor drum f, which faces the developing roller a at a minute interval of about 0.25 degrees, that is, toward the electrostatic latent image.
flies, and the electrostatic latent image becomes visible.

The toner t remaining on the developing roller a without flying away is collected into the container d by the urethane blade g, and then scraped off by the elastic foam roller b. Then, the elastic foam roller b1 passes under the aluminum roller C and returns to the toner reservoir above the aluminum roller C.

However, some problems still remain with such non-magnetic component developing devices.

First, the development margin is too small. It has been stated that the developing bias is 1.4 KV, but if this becomes 1.6 KV, discharge will occur and the image will become smudged. Also, 1.2
When it became KV, there was a problem that the image became thin.

Secondly, for example, if there is a scratch on the photoreceptor drum,
It is known that when toner locally bulges, a discharge pattern appears. however,
If the insulating material is coated with an insulating material such as Teflon in an attempt to increase the withstand voltage, there is a problem that the insulating material becomes electrically charged and attracts the toner due to Coulomb force, making it impossible for the toner to fly.

(Problems to be Solved by the Invention) As described above, in the conventional non-magnetic component developing device,
There were problems in that the margin for discharge could not be widened and it was difficult to obtain a uniform and free C degree development state.

The present invention has been made to solve the above problems, and its purpose is to form a developer layer on the developer holder by bringing a layer forming member into pressure contact with the developer holder, and to form a developer layer on the developer holder. In the developing device, which develops the electrostatic latent image formed on the image carrier, the margin against discharge is widened, and the margin against discharge is widened, and the density is stable against the environment, and uniform and free. It is an object of the present invention to provide a developing device that can obtain the following developing state.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention forms a developer layer on the developer holder by bringing a layer forming member into pressure contact with the developer holder. In this developing device, the surface of the developer holder is coated with a material having a resistivity of 10 3 to 1 QII Ω· in a developing device that develops the developer layer while facing the electrostatic latent image formed on the image carrier.

(Function) That is, according to the present invention, by coating the surface of the developer holder with a material having a specific resistance of 10' to 1011 Ωcm, the developer holder has a resistance that does not allow the current density to maintain the discharge to flow. It becomes a semiconductor with a breakdown voltage of IKV or higher. This results in
The margin for discharge is widened, and a uniform and free density development state can be obtained. Furthermore, it can be realized with an extremely simple structure, such as by coating with a material such as semiconductor glass or 5iC1A-Si.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 2 shows the configuration of a full-color laser printer employing the developing device of the present invention, and 1 in the figure is the main body of the device. At the upper center of the apparatus main body 1 is a photoreceptor drum 2 whose surface is coated with an organic photoreceptor as an image carrier.
A charging device 3, a multicolor developing device 4, a transfer drum 5, a cleaning device 6, and a static eliminating device 7 are provided around the photosensitive drum 2 along the rotation direction (arrow E direction). are arranged in sequence. Furthermore, a laser exposure device 8 for exposing image information is provided in the upper part of the main body 1 between the charging device 3 and the developing device 4. The multicolor developing device 4 is configured to include development band units 4a to 4d containing yellow, magenta, cyan, and black non-magnetic component developers (referred to as toners) t.

Further, a paper feed cassette 10 containing paper P such as plain paper is attached to one side of the apparatus main body 1, and a paper feed means 1
1, the sheets are fed one by one.

Paper P fed from the paper feed cassette 10 is conveyed along a U-turn conveyance path 12 and guided to a paper discharge tray 13 mounted above the paper feed cassette 10. The transfer drum 5, the peeling means 14, and the fixing device 15 are opposed to the U-turn conveyance path 12.

During image formation, the photoreceptor drum 2 rotates in the direction of arrow E, and the surface of the photoreceptor drum 2 is uniformly negatively charged by the charging device 3.

Thereafter, the image information is exposed by the laser exposure device 8, and the charge on the surface of the photoreceptor drum 2 is selectively removed to form an electrostatic latent image.

Accordingly, this electrostatic latent image is transferred to the developing device unit 4a (which contains the preset first color toner t of the developing device 4).
4b, 4c, and 4d), the charged non-magnetic component developer (toner) t is deposited and visualized by a non-contact jumping method.

On the other hand, at this time, the transfer drum 5 has a paper feed cassette/soto 10.
The paper P fed from the gripper 5a is wrapped around the gripper 5a with its leading end held by the gripper 5a. Then, the transfer drum 5 rotates in the direction of arrow F while a positive bias is applied, and the toner image on the photosensitive drum 2 is transferred onto the paper P at a transfer position A point.

Note that the toner t that has not been completely transferred is cleaned up by the cleaning device 6, and the memory of the photosensitive drum 2 is removed by the static eliminator 7, and the next cycle begins.

Here, when transferring a plurality of colors, the transfer drum 5 is rotated once again, and during this period, the second color developer unit 4b (4c, 4d) of the developing device 4 is transferred.

4a) are sequentially switched to face the photoreceptor drum 2.

After the transfer has been performed a predetermined number of times in this manner, the peeling means 14 operates to peel the paper P from the transfer drum 5 and enters the paper ejection process. Then, the fixing device 15 fixes the paper P.
The upper toner image is heated and fixed, and the paper is discharged onto the paper discharge tray 13.

Next, the configuration of the developing unit 4a of the multicolor developing device 4 will be explained. Note that other developing unit 4b,
4c and 4d also have the same configuration as the developing device unit 4a, so their explanation will be omitted.

The developing device unibutton 4a as a rack device of the present invention is as follows:
The configuration is as shown in Figure 3. In the figure, reference numeral 20 denotes a casing, and within this casing 20 is provided a developing roller 21 as a developer holding member that faces the photosensitive drum 2 with a minute gap G of about 0.25 mm therebetween. This developing roller 21 is placed on the surface of a stainless steel sleeve.
600 sandblasted material is used.

Further, on the casing 20, there is a urethane sponge in rolling contact with the developing roller 2), where an elastic foam roller 22 such as foamed rubber is placed, and furthermore, there is an aluminum sponge in rolling contact with the elastic foam roller 22. The rollers 23 are now placed.

Further, a stainless steel blade 24 having a thickness of 0.15 mα as a layer forming member is placed in pressure contact with the upper part of the developing roller 21, and a urethane blade 25 is in pressure contact with the lower part of the developing roller 21.

Note that 26 is a lid member, and 27 and 27 (only one of which is shown) are side frames.

Moreover, the stainless steel blade 24 as a layer forming member is
The upper edge portion is held by a blade holder 28 serving as a holding body, and is arranged parallel to the developing roller 21 .

The blade holder 28 is rotatably supported around support shafts 30 attached to both ends in the longitudinal direction, and is a press-contact member screwed into a stay 31 horizontally suspended between the side frames 27 and 27. When the upper surface is pushed by the force J3] adjustment 32.32, it is rotationally displaced in the direction of arrow B in FIG. Then, press contact force adjustment screw 3
2 and 32 can be tightened using stainless steel blade 24 depending on the condition.
The pressing force against the developing roller 21 can be adjusted.

Further, the developing roller 21, the elastic foam roller 22, and the aluminum roller 23 are driven via a driving force transfer system (not shown).

Positioning rollers (not shown) are coaxially attached to both ends of the developing roller 21, and the developing unit 4a
The positioning roller rolls into contact with the photosensitive drum 2 by being urged to rotate about the shaft 35 as a whole, so that the predetermined gap G can be secured.

Thus, the non-magnetic component toner t that has entered the casing 20 is carried to the right in FIG. roller 21
It is sent between the stainless steel blade 24 and the stainless steel blade 24 that comes into pressure contact with the stainless steel blade 24. Here, the toner t is made into a thin layer, charged, and sent to the photosensitive drum 2 side.

At this time, the developing roller 21 is supplied with -250V and AC voltage.
Since a bias of 4 KV is applied, the toner t flies toward the exposed portion of the photoreceptor drum 2 facing the developing roller 21 with a minute gap G, that is, toward the electrostatic latent image.
The electrostatic latent image becomes visible.

Note that toner t remaining on the developing roller 21 without flying away
is collected into the casing 20 by the urethane blade 25 and then scraped off by the elastic foam roller 22. The toner then passes under the elastic foam roller 22 and aluminum roller 23 and returns to the toner reservoir 36 above the aluminum roller 23 .

Further, in the present invention, a semiconductor coating layer 40 is formed on the surface of the developing roller 21 as a developer holder. This coating layer 40 has a specific resistance of 103 to 10
It is made of a material with a resistance of 11 ohms, and has a resistance that does not allow the flow of current density to maintain discharge, and has a withstand voltage of IKV or higher. This widens the margin for discharge, making it possible to obtain a uniform and free density development state.

To see the specific resistance value, use the lowest value of glow discharge as a guide.

When the material is Cu, it is 240 μA / cm 2 (A+er1ean In5t1tutco
f' Physics Han-dobook) R> 15/240-0.25X 106Ω・crn2 because the current higher than the above does not flow when the voltage is lowered by 1.5KV
=il).

Further, in order to estimate the upper limit of the resistance value, the attenuation time constant is set to be one period or less of the developing roller 21.

Capacity per unit area -eEos S: Thickness of the coating layer, 50 μm as a first approximation
shall be.

ε: Relative dielectric constant, set to 1.

ε. : Dielectric constant of vacuum C-8,85X 10-14150X 10-'-1'
1.7cyF/cm2d: The diameter of the developing roller is 20Φ.

The circumferential speed of the developing roller is 100 m+s/see.

From (2) becomes.

Therefore, from the viewpoint of wear resistance, for example, semiconductor glass, SiC, A-8i, etc. are suitable.

Further, in the case of semiconductor glass, the coating layer 40 is formed by applying a water glass-like semiconductor glass and then performing a baking process. In the case of SiC, a CVD (vapor phase growth) method is used, and in the case of A-Si, a sputtering method is used.

According to this invention, as described above, the specific resistance formed on the surface of the developing roller 21 is 103 to 10'1Ω·ctlI.
(more preferably 107 to 10" Ω・Cm), the coating 40 is made of a material with a resistance that does not allow the current density that maintains the discharge to flow, that is, the withstand voltage is IKV.
That's all.

Therefore, the margin for discharge is widened, and a uniform and free density development state can be obtained.

Furthermore, environmental resistance is improved, for example, measures are taken to prevent uneven development caused by discharge when atmospheric pressure drops at high altitudes.

Note that the present invention is not limited to the above-mentioned embodiment. For example, the gap G between the developing roller 21 and the photosensitive drum 2 is set to 0.
Although the explanation has been made assuming that the length is 25 meters, the environmental resistance can also be improved by making this smaller, for example, 0.12 m+*.

This is because although the developing bias can be kept small by making the gap G small, the discharge limit value does not become so small.

In addition, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As explained above, according to the present invention, a layer forming member is brought into pressure contact with a developer holder to form a developer layer on the developer holder, and this developer layer is attached to an image carrier. The developing device, which develops the electrostatic latent image formed in the opposite direction, has a simple structure but has a wide margin against discharge, is stable against the environment, and can achieve a uniform and free density development state. This has the advantage that it is possible to provide a developing device that can be obtained.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention,
FIG. 1 is a schematic diagram of the developing device, FIG. 2 is an internal diagram of a full-color printer employing the developing device of the present invention, FIG. 3 is a partial sectional view of the developing roller, and FIG. 4 is a conventional example. FIG. 2... Image carrier (photosensitive drum) 4a to 4d...
・Developing device (developing device unit), 21... Developer holding body (developing roller), 24... Layer forming member (stainless steel blade), 40... Covering layer, t... Developer (toner) .

Claims (1)

[Claims] In a developing device that forms a developer layer on the developer holder by bringing a layer forming member into pressure contact with the developer holder, and develops this developer layer by facing an electrostatic latent image formed on an image carrier. ,
The surface of the developer holder has a specific resistance of 10^3 to 10^11Ω.
A developing device characterized in that it is coated with a material of cm.